1. Field of the Present Invention
The present invention relates to a resin composition, and more particularly, to a resin composition having halogen-free, flame-retardant and high thermal conductive capable of being formed as a dielectric layer on a printed circuit board (PCB).
2. Description of Related Art
For making a traditional UL94-V0 flame-retardant FR4 printed circuit board (PCB), reaction between tetrabromobisphenol and a plethora of epoxy resin is implemented to obtain a resin with two end-epoxy groups that is further mixed with a curing agent and an accelerant to form a prepreg to be constructed upon glass fiber cloth before thermally hardened so as to endow the PCB with flame retardancy. Alternatively, tetrabromobisphenol may be mixed with other epoxy hardeners before joining the cure reaction with epoxy resin, so as to produce cured epoxy resin that is flame-retardant. Since tetrabromobisphenol is a halogen flame retardant, it emits dioxin or benzofuran and other irritant, corrosive pernicious gases when burning. In addition, a low-molecular-weight smoke suppressing agent tends to deteriorate the resulting material by weakening mechanical properties and photolysis thereof. Also, the transfer and volatility of the smoke suppressing agent in the material may have adverse effects on the physical properties and flame retardancy of the material.
Recently, with the trend toward high-density integrated circuit configuration, accumulation of heat generated from electronic components tends to aggravate and thus conventional epoxy resin becomes inadequate for IC applications in respect of thermal conductivity. While an insulating layer (also known as a dielectric layer) applied to a metal base board has been disclosed in Japan Patent No. 05-267808 for improved thermal conductivity, the aforementioned material is unproven as UL94-V0 rating flame-retardant and has its application limited to single-layer boards only. On the other hand, although U.S. Pat. No. 6,187,416 has disclosed a halogen-free, phosphorous-free resin, it does not state whether the resin has high thermal conductivity and conforms with the UL94-V0 flame-retardant standard.
In view of the shortcomings of the prior arts, there is a need for a halogen-free, flame-retardant and high thermal-conductive resin composition for being applied to PCBs so as to answer to the request of modern electronic products where compactness and integrity are required.